The practice of placing milled lumber pieces, or boards, into orderly stacks of predetermined sizes has long been known to facilitate storage, transportation, and handling of the lumber. Further, the stacking of lumber pieces in certain manners is known to enhance various lumber processing operations such as lumber drying and curing and the like. Specifically, the stacking of lumber pieces, wherein the pieces are spaced apart from one another within the stack to allow for air circulation between the lumber pieces, is known to promote efficiency of lumber drying operations, and especially of operations wherein drying kilns are employed.
In relatively recent times, automatic lumber stacking apparatus have been developed to increase production capacity and efficiency, as well as to avoid the tedium and safety risk associated with the manual stacking of lumber pieces. The general nature of a typical prior art lumber stacking apparatus can be easily understood by an examination of U.S. Pat. No. 4,057,150 to Lunden. As a study of the '150 patent reveals, the operation of a typical prior art automatic lumber stacking apparatus can be generally described as in the following paragraphs in conjunction with the FIG. 1 of the subject patent.
Referring to FIG. 1 of the '150 patent, the lumber pieces 12 to be stacked are brought into the lumber stacking apparatus 10 on a lumber in-feed conveyance means 25. The lumber in-feed conveyance means 25 can have any of a number of acceptable and known forms, including a drag-chain conveyor, for example. The lumber pieces 12 are staged and accumulated in a single-layer course at a pickup station 15 to await transfer from the pickup station 15 to a stacking station 18 where a lumber stack 16 is formed.
A fork assembly 51 lifts the accumulated course of lumber pieces 12 from the lumber conveyance means 25 at the pickup station 15 and moves the course of lumber pieces to a stacking station 18, where the course is deposited on a hoist platform 17. The course of lumber pieces 12 is typically removed from the fork assembly 51 by way of a stationery rake-off device (not shown) which is synchronously deployed relative to the movement of the fork assembly, the result of which is to strip the course off of the fork assembly as the fork assembly moves away from the stacking station 18 and back toward the pickup station 15. The prior art rake-off device will be described in further detail in later discussion.
The above-described process of moving the lumber pieces 12 from the pickup station 15 to the stacking station 18, wherein successive courses of lumber pieces 12 are placed one upon the other by the fork assembly 51, is repeated as often as necessary to form a lumber stack 16 of desired size on the hoist platform 17. The hoist platform 17 is generally configured to move the stack 16 incrementally downward in synchronous correspondence with placement of each successive lumber course thereupon so as to maintain the top surface of the stack at a substantially constant elevation relative to the path of the fork assembly 51. Upon formation of a lumber stack, the completed stack is removed from the hoist platform 17, and formation of a new stack is commenced thereupon.
As mentioned briefly above, it can be desirable to cause successive courses within a given lumber stack to be spaced apart from one another in order to promote drying processes and the like. Such spacing of successive courses of lumber within a given lumber stack is typically accomplished by placing spacers between the lumber courses that are to be spaced apart. The spacers are often in the form of relatively small lumber strips that are referred to in the art as “stickers.” While the placement of stickers during the formation of a lumber stack can be accomplished manually, it is obviously desirable to perform sticker placement automatically in conjunction with the operation of an automatic lumber stacking apparatus.
Accordingly, some prior art lumber stacking apparatus incorporate automatic sticker placers that operate in conjunction therewith to automatically form a lumber stack having spaced apart courses. Prior art sticker placers of a variety of configurations have been developed. The U.S. Pat. No. 4,253,787 to Lunden discloses at least two types of sticker placers. One type of prior art sticker placer can be understood by an examination of FIGS. 6, 7, 8, and 9 of the '787 patent. With reference thereto, a sticker in-feed conveyance means 73 is employed which can be in the form of an endless lug chain conveyor as depicted. Such a lug chain conveyor typically comprises a plurality of lugs which are spaced at predetermined intervals, the purpose of which is to facilitate control of the location of the stickers 15 on the sticker in-feed conveyance means 73.
Stickers 15 are moved from a sticker hopper (not referenced) or the like and into the pickup area (not referenced) and underneath the fork assembly 24 by way of the sticker in-feed conveyance means 73. The path of movement of the stickers 15 on the sticker in-feed conveyance means 73 is generally transverse with respect to the operational path of movement of the fork assembly 24 as well as to the movement of the lumber pieces 12 on the lumber in-feed conveyance means 18. The fork assembly 24 includes a plurality of individual fork arms 25. Each of the fork arms 25 has at least one sticker tray 84 attached thereto on which a sticker is to be placed.
A sticker transfer means 80 is employed to transfer stickers from the sticker in-feed conveyance means 73 to the sticker trays 84, wherein one sticker is placed in each of the sticker trays. The sticker transfer means 80 includes a number of frame members 87, 88 that are connected to one another in a rigid manner. The sticker transfer means 80 also includes several pairs of flat support brackets 86 that are rigidly connected to the frame members 87, and are configured to contact a corresponding sticker 15 and lift the sticker off of the sticker in-feed conveyance means 73 in response to movement of the frame members 87, 88 in an upward direction relative to the sticker in-feed conveyance means.
After the stickers 15 are lifted off of the sticker in-feed conveyance means 73 by the sticker support brackets 86, the stickers are held in a stationary position until the upward movement of the fork assembly 24 causes the corresponding sticker tray 84 to contact the respective sticker and to lift the sticker from the support brackets. After lifting the sticker 15 from the sticker transfer means 80, the fork assembly 24 then moves upwardly to contact the lumber pieces 12 which are staged thereabove upon the lumber in-feed conveyance means 18. The stickers 15 are thereby sandwiched between the respective sticker tray 84 and the lumber pieces 12 as the lumber pieces are lifted off of the lumber in-feed conveyance means 18 by upwardly movement of the fork assembly 24. The course of lumber pieces 12 is then placed upon a previously formed course of lumber pieces along with the stickers 15 which are located there between.
The sticker transfer means 80 functions by way of the frame members 87, 88 are caused to move along an arcuate path by way of a plurality of bellcranks 90 which are pivotally connected to the frame members 88 and to a shaft 89 that is rotationally supported on a framework 18. The shaft 89, in turn, is rigidly connected to a primary bellcrank 91 which is pivotally connected to a linkage 92 that is operatively supported on the framework 18. At least two shafts 89 are employed in the manner shown, wherein the shafts, together with the frame members 87, 88 and associated bellcranks 90 operate in the manner of a parallelogram four-bar-linkage.
The linkage 92 can be actuated by any of a number of actuating means, such as by way of the cam surface 94 and respective cam follower 93 as shown. However, as explained in the '787 patent, the linkage 92 is preferably actuated by a fork assembly actuating means (not referenced) so as to maintain synchronicity of movement with respect to the sticker transfer means 80 and the fork assembly 24. That is, by configuring the linkage 92 and the fork assembly 24 to be actuated by a common actuating means, the operation of the sticker transfer means 80 is synchronized with that of the fork assembly 24.
Another prior art form of sticker placer which is disclosed in the '787 patent can be understood by a close examination of FIGS. 10, 11, 12, 13, and 14. As shown in those figures, the sticker placer disclosed thereby includes a sticker in-feed conveyance means 73 as well as a sticker transfer means 80. While the sticker in-feed conveyance means 73 can be identical, or at least substantially similar, to that of the sticker placer described immediately above, the sticker transfer means 80 which is shown in FIGS. 10 through 14 of the '787 patent is substantially dissimilar to that of the sticker placer described immediately above.
As is seen in FIGS. 10 through 14 of the '787 patent, the sticker transfer means 80 shown therein comprises a pair of elongated, endless conveyer members 190 that are arranged so as to operate in a substantially convoluted, serpentine circuitous path. Additionally, the sticker transfer means 80 includes a series of substantially flat support brackets 86 which are connected a regular, predetermined intervals to a respective conveyor member 190. Each of the conveyor members 190 can be circulated about its respective path by way of a drive means 194.
As is seen, the path of each respective conveyor member 190 is established by way of various guide and drive sprockets 200, 201, 203, which are operatively located at precisely determined stationary positions relative to the fork assembly 24. The movement, along the respective circuitous paths, of the conveyor members 190 causes the respective support brackets 86 attached thereto to thereby contact and lift the stickers 15 off of the sticker in-feed conveyor means 73 and then to deposit the stickers upon the respective sticker trays 84 which are connected to each respective fork arm of the fork assembly 24. In this manner, the stickers 15 are moved from the sticker in-feed conveyance means 73 to the respective sticker trays 84, from whence the stickers are placed between successive courses of lumber pieces in conjunction with the formation of a stack of lumber.
Yet another form of sticker placer is disclosed by U.S. Pat. No. 4,324,521 to Lunden. The sticker placer of the '521 patent can be understood by a study of FIGS. 3, 4, 5, 6, and 7 thereof. With reference now to FIG. 3 of the '521 patent, the stickers 14 are brought into proximity with the respective fork arms 25 of a stacking apparatus by way of the sticker in-feed conveyance means 16. The sticker in-feed conveyance means 16 can be operatively supported on a stationary frame 15. The frame 15 comprises a vertical flange (not referenced) as well as a horizontal flange 47.
A series of rollers 29 as well as a series of pivots 44 are also each operatively supported on the frame 15. A carriage 28 is operatively disposed upon the series of rollers 29 so as to be movable along a horizontal path which is substantially parallel to the both the frame 15 and the sticker in-feed conveyance means 16. An actuating means (not shown) is employed to move the carriage 28 in a reciprocating motion while supported on the series of rollers 29. A sticker tray 27 is mounted on each fork arm 25, and is configured to receive and support a sticker 14.
A series of pivot shafts 38 are rotationally supported on the carriage 28 so as to pivot with respect thereto. A pair of spaced sticker support arms 40, as well as at least one crank arm 50, are rigidly connected to each pivot shaft 38. A cam roller 49 is rotationally mounted on one end of the crank arm 50 and is configured to be supported on the horizontal flange 47 of the frame 15, and to roll there along during movement of the carriage 28 with respect to the frame. A ramp 43 is rigidly connected to each pivot 44 so as to be pivotable along therewith relative to the frame 15. The cam roller 49 and the ramp 43 are positioned relative to one another, wherein movement of the carriage 28 causes the cam roller to move toward the ramp and to engage the ramp, whereupon the cam roller is caused to roll upwardly upon the inclined surface 45 provided by the ramp.
The FIGS. 4 through 7 of the '521 patent depict an operational sequence of the sticker placer disclosed thereby. As shown in FIG. 4 of the '521 patent, the cam roller 49 is supported upon the horizontal flange 47 of the frame 15. A sticker (not referenced) is shown to be supported on the sticker in-feed conveyance means 16. The fork arm 25 and associated sticker tray 27 are also shown to be positioned above the sticker in-feed conveyance means 16. The carriage 28 is poised so as to be moved horizontally to the right, whereby the cam roller 49 will be caused to move toward the ramp 43.
Moving now to FIG. 5 of the '521 patent, it is seen that the carriage 28 has moved to the right, whereby the cam roller 49 has been caused to roll upwardly upon the inclined surface 45 of the ramp 43. Moreover, the cam roller 49 has moved past the pivot 44, and has begun to move downwardly upon the declined surface 51 of the ramp 43. As is further seen, the rightward movement of the carriage 28, and the resulting movement of the cam roller 49 upon the ramp 43 has caused the sticker support arm 40 to pivot in a clockwise direction, whereby the sticker 14 has been contacted and lifted upwardly thereby from the sticker in-feed conveyance means 16.
As depicted, the support arm 40 is poised to deposit the sticker 14 upon the sticker tray 27 with further rightward movement of the carriage 28. That is, further rightward movement of the carriage 28 will cause the cam roller 49 to drop off the end of the ramp 43 so as to come to rest upon the horizontal flange 47 of the fame 15, in turn resulting in counterclockwise rotation of the support arm 40. Such counterclockwise rotation of the support arm 40, along with the continued rightward movement of the carriage 28 will cause the sticker 14 to be deposited into the sticker tray 27 as the cam roller 49 continues downward to come to rest upon the horizontal flange 47 of the frame 15.
With reference now to FIG. 6 of the '521 patent, the cam roller 49 is depicted as having dropped from the ramp 43 so as to come to rest upon the horizontal flange 47 of the frame 15. The carriage 28 is now poised to move leftward on a return leg of its reciprocating cycle of movement. As is seen, during such leftward movement of the carriage 28 relative to the frame 15, the cam roller 49 will be caused to roll upon the horizontal flange 47 of the frame.
Moving now to FIG. 7 of the '521 patent, the purpose of the pivotal nature of the ramp 43 and pivot 44 is apparent. That is, as the leftward movement of the carriage 28 continues, the cam roller 49 contacts the lower surface 46 of the ramp 43 so as to cause the ramp to pivot in a clockwise direction about the pivot 44. The cam roller 49 thereby passes beneath the ramp 43 by pushing the ramp upward. As the leftward movement of the carriage 28 continues, the cam roller 49 passes the end 52 of the ramp 43, whereupon the ramp reverses its movement and pivots in a counterclockwise direction under the force of gravity so as to return to a rest position, wherein the end is in contact with the horizontal flange 47 of the frame 15. The carriage 28 continues its leftward movement until it achieves the relative position depicted in FIG. 4, from whence the cycle described above is repeated to place another sticker 14 into the sticker tray 27.
Still another form of sticker placer is disclosed by U.S. Pat. No. 5,720,592 to Gillingham et al. The sticker placer of the '592 patent can be understood by an examination of FIGS. 8 and 9 thereof. As depicted in FIGS. 8 and 9, the stickers 73 are brought into proximity with the fork arms 32 by way of the sticker in-feed conveyance means 21. A respective sticker tray 22 is pivotally connected to each fork arm 32 by way of a respective hinge 93. A respective pivot arm 98 is rigidly connected to each sticker tray 22. A linkage 100 is operatively connected to each pivot arm 98, as well as to an actuator 103, wherein actuation of the actuator causes pivoting of the sticker trays 22 by way of the linkage and respective pivot arm.
Thus, when the respective stickers 73 have approached to within a given proximity of the corresponding sticker tray 22, a first actuation of the actuator 103 causes the sticker trays to pivot downward. The movement of the sticker in-feed conveyance means 21 continues so as to position the respective stickers 73 substantially above the corresponding sticker trays, wherein a second actuation of the actuator 103 opposite the first actuation causes the sticker trays to pivot upward, whereby, together with upward motion of the fork arms 32, the respective stickers are cradled within the corresponding sticker tray and lifted upwardly from the sticker in-feed conveyance means.
As mentioned briefly above, a rake-off, or stripping, device is typically employed in conjunction with prior art stacking apparatus to facilitate transfer of lumber pieces from the fork assembly to the stack. Returning now to the '787 patent, a typical rake-off device is disclosed therein. The rake-off device of the '787 patent can be understood from an examination of FIGS. 3, 4, and 5. Referring to FIGS. 3, 4, and 5 of the '787 patent, the rake-off device 56 typically includes at least one cross bar 61 that is oriented transversally relative to the fork arms 24 of the fork assembly 25. The cross bar 61 is typically suspended from overhead by way of a chain 63. The movement of the cross bar 61 is typically restricted to a substantially vertical path.
The chain 63 is typically employed to control the movement of the cross bar 61, wherein the cross bar is selectively moved between a lower stripping position and an upper clear position in synchronization with the movement of the fork assembly 25. That is, as the fork assembly 25 moves the lumber pieces 12 from the pickup station (not shown) to the stacking station (not shown), the cross bar 61 remains in the clear position, wherein the lumber pieces and fork assembly pass unheeded beneath the cross bar. However, when the fork assembly 25 reaches its fully extended position above the stack at the stacking station, the cross bar 61 is typically deployed by lowering from the clear position into the stripping position.
When deployed in the stripping position, the cross bar 61, by way of a plurality of spaced stripping surfaces 68 attached thereto, prevents further movement of the lumber pieces 12 while the fork assembly 25 moves back toward the pickup station. That is, the cross bar 61, while suspended by the chain 63, is lowered into the stripping position after the fork assembly 25 and the lumber pieces 12 have reached the stacking station, but before the fork assembly returns to the pickup station. The cross bar 61 and associated stripping surfaces 68, while in the stripping position, are strategically located relative to the fork arms 24 such that the fork arms can pass freely back to the pickup station, while the lumber pieces 12 are prevented, by way of contact with the stripping surfaces, from movement toward the pickup station. In this manner, the lumber pieces 12 are raked, or stripped, from the fork arms 24 as the result of the withdrawal of the fork assembly 25 from the stacking station. The course of lumber pieces 12 is thus deposited at the stacking station to form a stack of lumber pieces.
The stickers (not shown) are typically raked, or stripped, from the associated sticker trays in a similar manner. That is, the rake-off device is deployed between strokes of the fork assembly so as to contact the stickers and thereby rake the stickers from the sticker trays as the fork arms and sticker trays are withdrawn from the stacking station on the return stroke of the fork assembly.
Although prior art sticker placers and rake-off devices such as those described above have been known to perform satisfactorily, it can be appreciated that certain disadvantages can be associated with the configurations thereof. Specifically, the complex design and high parts-count of the prior art sticker placers can result in expenditures of excessive quantities of resources toward the resolution of maintenance and repair issues. For example, a tolerance buildup due to degradation and wear of interconnected components of a typical prior art sticker placer can lead to unacceptable performance which can be remedied only by extensive overhaul and rework of the components.
Furthermore, the form and configuration of the prior art sticker placers can tend to limit the usefulness thereof. For example, the prior art sticker placers are generally not capable of removing stickers from the sticker trays once the stickers are deposited in the trays. This can prove disadvantageous in the event that the stickers must be removed from the trays. Removal of stickers from sticker trays in prior art apparatus typically requires that the entire stacking apparatus and associated components be shut down and that a safety lockout of the apparatus be performed in preparation for manual removal of the stickers.
As another example of the limiting nature of the prior art sticker placer configurations, the stroke of movement of the prior art configurations is generally limited, thus limiting the depth of the fork arms with which the sticker placer can be employed. That is, as stacking apparatus increase in size and capacity, the depth of the fork arms is generally required to increase.
Such an increase in the depth of the fork arms requires that the stickers be lifted a greater distance from the sticker in-feed conveyance means to the sticker trays. However, due to the prior art sticker placer configurations are limited with respect to the stroke of movement, and thus the distance of which the stickers can be lifted from the sticker in-feed conveyance means.
Moreover, disadvantages can be similarly associated with the configurations of prior art rake-off devices. Specifically, the configuration of such prior art rake-off devices limits the precision and speed with which the rake-off device can be positioned relative to the fork arm and sticker trays, thus limiting the overall operational speed and efficiency of the associated stacking apparatus.
What is needed then are information system methods and apparatus which achieve the benefits to be derived from similar prior art methods and/or devices, but which avoid the shortcomings and detriments individually associated therewith.